Protective Undergarment

ABSTRACT

A protective undergarment for use under casual clothing is described. The undergarment is constructed of a first impermeable barrier material and a second selectively permeable barrier material.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a thin, chemical and biological protective garment providing improved heat loss, and which is substantially undetectable under clothing.

2. Description of Related Art

While many barriers are referred to as chemical protective barriers, there exists a variety of materials providing a range of protection levels, such as those offering a low level of liquid penetration resistance and others which are impermeable to toxic vapors and liquids. Overgarments made from materials which are impermeable to toxic vapors and liquids, provide an effectively high level of chemical and biological protection. A construct which is capable of providing a particularly high level of chemical and biological protection includes a thick, impermeable plastic barrier. Disadvantageously, barriers providing the highest level of chemical and biological protection are stiff and thick, and garments made from them are often heavy and bulky. These garments are therefore unsuitable for inconspicuous use or use under clothing. Commonly used impermeable barriers providing chemical and biological protection are often resistant to the transport of water vapor and create thermal stress for wearers after extended use and/or in hot environmental conditions, and thus, similarly unsuitable for use under clothing.

Different approaches have been used to address the comfort of a person wearing suits formed from impermeable barrier material. For example, a loose-fitting, impermeable suit constructed of a fluid impermeable barrier material may incorporate air permeable panels to provide ventilation. For example, a coverall may be provided with air permeable gussets to the arm pits and crotch for ventilation. Air is drawn in as the movement of the wearer creates a bellowing effect of the loose overgarment, cooling the wearer. Alternately, air may be supplied by a cooling air system which circulates supplied air. While providing cooling, air permeable portions are vulnerable to the entry of hazardous fluids.

Protective garments formed of selectively permeable materials may provide lower levels of protection compared to impermeable, and selectively permeable materials are often thick and stiff. Adsorbent-based materials often have an outer shell layer of liquid repellant material and an inner adsorptive layer (typically activated carbon) to filter out chemical vapors permeating through the thickness.

The aforementioned characteristics render protective garments that provide a high level of chemical and biological protection unsuitable for undetectable use under casual, non-operational clothing due to bulk and stiffness, and are unsuitable for extended wear due to heat stress.

For individuals who would benefit from high level chemical and biological protection while wearing casual, or non-operational clothing, there has been a long-felt need for a garment which is sufficiently thin and flexible to wear undetectably under non-protective or causal clothing, while providing sufficient thermal comfort for extended wear and wear in unfavorable environmental conditions. Accordingly, it is desirable to have a chemical and biological protective undergarment which maximizes protection, provides sufficient cooling for extended wear, and is substantially undetectable under casual or non-operational clothing.

SUMMARY OF THE INVENTION

One embodiment of the present invention is an article comprising a protective undergarment for use under casual clothing. The garment comprises a top and bottom portion and the garment surface covers the arms, legs, and torso of a wearer.

About 55% to about 95% of the garment surface area is formed from a first impermeable barrier material comprising air impermeable, moisture vapor impermeable fluoropolymer. Complementally, about 5% to about 45% of a garment surface area is formed from a second selectively permeable barrier material comprising an air impermeable, moisture vapor permeable expanded polytetrafluoroethylene (ePTFE) composite. The second selectively permeable barrier material is located at discrete regions on the back garment surface corresponding to the wearer's torso and/or legs. The second barrier material is in the form of a panel integrally included as part of the garment construction, and joined to the first barrier material by a seam.

Each of the first and second barrier materials passes NFPA 1971 ASTM F903 (Standard Test Method for Resistance of Protective Clothing Materials to Penetration by Liquids) chemical penetration tests, which have a requirement of no visible liquid penetration for at least one hour.

DESCRIPTION OF THE DRAWINGS

The operation of the present invention should become apparent from the following description when considered in conjunction with the accompanying drawings, in which:

FIG. 1 is a diagrammatic representation of a front view of one embodiment of the present invention.

FIG. 2 is a diagrammatic representation of a back view of one embodiment of the present invention.

FIG. 3 is a cross-sectional representation of a first impermeable barrier material of one embodiment of the present invention.

FIG. 4 is a cross-sectional representation of a second selectively permeable barrier material of one embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

In accordance with one embodiment of the present invention, as exemplified in FIGS. 1 and 2, an undergarment 10 is provided having a top part 11 and bottom part 12 which substantially covers the arms, legs, and torso of a wearer and which provides a high level of chemical and biological protection under casual clothing. The undergarment comprises a first impermeable barrier material 30 comprising an air impermeable, moisture vapor impermeable (non-breathable) material and a second selectively permeable barrier material (FIG. 2 at 40) comprising a material which is air impermeable, moisture vapor permeable.

In one embodiment, the undergarment is constructed having a garment surface wherein about 55% to about 95% of the garment surface area comprises the first impermeable barrier material. Complementally, about 5% to about 45% of the garment surface is comprised of the second selectively permeable barrier material. Constructs having from about 70% to about 95% of the garment surface area comprised of the first impermeable barrier material, while complementally about 5% to about 30% of the garment surface area comprises the second selectively permeable barrier material, are also suitable for use in the present invention. Moreover, constructs having from about 80% to about 95% garment surface area comprising the first impermeable barrier material, while complementally about 5% to about 20% of the garment surface area comprises the second selectively permeable barrier material, are also suitable for use. Further, where greater protection from liquid penetration is desired, constructs having from about 85% to about 95% garment surface area comprising the first impermeable barrier material, while complementally about 5% to about 15% of the garment surface area comprises the second selectively permeable barrier material, are also suitable for use in the instant invention. Constructs having greater than 90% of the garment surface area comprising the first impermeable barrier material, while complementally less than about 10% of the garment surface area comprises the second selectively permeable barrier material, are also suitable for use in this invention.

The undergarment is designed so that the first impermeable barrier material 30 offering greater chemical protection comprises a front garment surface 22 corresponding to the front surfaces of the wearer's arms, legs, and torso.

The garment is designed wherein the second selectively permeable barrier panel 40 is positioned on a portion of a back garment surface 21, and preferably corresponding to the wearer's back torso region. The garment may also be designed wherein the second selectively permeable material is a panel incorporated on a portion of the garment that additionally or optionally corresponds to the back of the wearer's legs. Where the second selectively permeable barrier material is located on a portion of the garment corresponding to the back of the wearer's leg, the material is located on a back thigh portion 40′, and additionally or optionally, on the portion of the garment corresponding to the back of a wearer's knee.

The first impermeable barrier material and the second selectively permeable barrier material portions of the garment can be joined together by any method known in the art for joining materials. However, it is preferred that first and second barrier materials are joined together in a manner that renders the seams between first and second barrier materials at least as impermeable to chemical and biologic threats as the second selectively permeable material portions. Panels can be joined at seams (13), for example, by sewing, taping, welding, and the like. Sewn seams may be taped with impermeable seam tapes.

Both first and second materials are air impermeable when tested according to the Gurley Test Method for air permeability described below.

Materials suitable for use as the first impermeable barrier material pass NFPA 1971 ASTM F903 (Standard Test Method for Resistance of Protective Clothing Materials to Penetration by Liquids) chemical penetration test. Some examples include but are not limited to thin, flexible polytetrafluoroethylene-based (PTFE) materials which have chemical and biological resistance. Non-porous, dense PTFE is one such example. Other suitable, impermeable barrier materials include polyurethane, polyethylene, polyvinylchloride, polyolefins, butyl rubber, chloropolymers, ethylenevinylalcohol, polyvinylidenechloride, and copolymers thereof.

In one example, a dense PTFE laminate, wherein the dense PTFE film is laminated to a polyester knit textile, is suitable for use in the present invention. Examples of such laminates are manufactured by W. L. Gore and Associates, Inc., under part number KPDX607000A and are hereby incorporated by reference herein. The first impermeable barrier material may further comprise additional layers such as additional textile layers. FIG. 3 exemplifies a multilayer first impermeable barrier material 30 for use in the present invention, comprising an air impermeable, moisture vapor impermeable barrier material 35, and a textile material, such as a knit or woven, which may be the same or different, and may be further attached to one or both sides of the barrier material 35. In one embodiment, for example, knit textile layer 37 may be attached to the side of the first barrier material 35 that faces away from the body of a wearer. Optionally, a second knit textile layer 38 may be attached to the first barrier material 35 on the side that faces towards the body of a wearer. The textile layers may be attached by known methods such as adhesive dots 34 and 34′. Where only one knit textile layer is provided to the impermeable membrane, garments may be constructed so that the knit side is facing either towards or away from the body of a wearer.

The second selectively permeable barrier material suitable for use in the present invention is moisture vapor permeable (i.e., ‘breathable’), air impermeable, and also passes the NFPA 1971 ASTM F903 (for Resistance of Protective Clothing Materials to Penetration by Liquids) chemical penetration tests. By moisture vapor permeable, or breathable, it is meant that the material has a moisture vapor permeability of at least 1,000 g/(m²*day), preferably greater than about 2,000 g/(m²*day), and more preferably greater than about 3,000. g/(m²*day) as measured by the test provided herein. By ‘non-breathable’ is meant materials having a transmission to moisture vapor of less than about 900 g/(m²*day). In one example, a monolithic polymer layer is used. Selectively permeable materials comprising selectively permeable membranes including polyamine polymers such as those membranes made substantially according to the teaching of commonly owned U.S. Pat. No. 6,395,383 to Maples, which is hereby incorporated by reference, are suitable for use in the present invention. Other suitable materials comprise polyurethane. The second selectively permeable barrier material may further comprise additional layers such as support layers to support the selectively permeable material. Expanded polytetrafluoroethylene (ePTFE) membranes may be incorporated into the second selectively permeable barrier material in addition to the selectively permeable polymer material. The second selectively permeable barrier material, comprising a selectively permeable membrane and an ePTFE membrane, has for example, a moisture vapor transmission rate greater than about 1,000 g/(m²*day), greater than about 2,000 g/(m²*day), greater than about, 3,000 g/(m²*day), or greater than about 4,000 g/(m²*day).

The second barrier material may further comprise a laminate of the selectively permeable material and an additional layer such as a woven, non-woven, knit, or scrim layer. In one example according to FIG. 4, a second selectively permeable barrier material 40 comprises a selectively permeable membrane layer 45, and further comprises an ePTFE membrane layer 46 and 46′ on each side of the selectively permeable material. The ePTFE layers provide support without reducing the moisture vapor permeability of the second selectively permeable barrier material. In FIG. 4, one additional layer 46 and 46′ is attached to each side of the membrane layer 45. FIG. 4 exemplifies the second selectively permeable barrier material having a knit textile 47 attached to a selectively permeable membrane 45 on the side facing away from the body of a wearer, and a second knit textile 48 attached to the selectively permeable membrane 45 on the side closest or towards the body of the wearer. The materials may be attached by lamination through, for example, adhesive dots 44 and 44′. Where only one knit textile layer is provided to the selectively permeable barrier material, garments may be constructed so that the knit side is facing either forward or away from the body of a wearer.

Garments made comprising first and second barrier materials which are suitable for use as undergarments and which are undetectable under casual clothing, are flexible and thin. For example, an undergarment comprising a garment top and bottom having a packed volume of less than about 0.0034 m³ is suitable for use under clothing. Other undergarments comprising a garment top and bottom according to the present invention for undetectable use under clothing have a packed volume (when tested according to the method described herein) of less than about 0.0042 m³ or less than about 0.0037 m³.

Undergarments of the present invention may further have an additional outer layer or sections (fascia), which have the appearance of casual, or non-operational, underclothing, integrated around visible portions of the garment. When worn with traditional outer clothing, for example, the fascia may be constructed of a collar portion, wrist portions, and the like to render the protective undergarment of the present invention further undetectable. Fascia suitable for use in the present invention may be made of material (cotton, cotton blends, and the like) suitable for casual or non-operational clothing, and may be in the form of, for example, tee-shirt or work shirt collar, cuff, and the like.

Overall weight of the construction of the present invention can vary widely depending on the desired performance characteristics of the articles. The material weight per unit area of the articles of this invention depends, among other factors, on the selection of the component materials used. Preferably, the articles of this invention have a material weight of less than about 20 oz/yd². Articles of the invention can also be made having a weight per unit area less than about 15 oz/yd², and less than about 10 oz/yd². Where weight is a significant factor in use and desirable constructions are those with lower weights, the overall weight of the article may be about 8 oz/yd² or less, or about 6 oz/yd² or less, or about 5 oz/yd² or less.

In one embodiment, an undergarment is formed for use under casual clothing wherein the undergarment covers the arms, legs, and torso of a wearer and has a heat loss of at least 20 w/M² at about 35° C. and about 50% RH when tested according to the method described herein for heat loss and evaporative resistance. In other embodiments, an undergarment is formed for use under casual clothing wherein the garment has a heat loss of at least 30 w/M² at about 35° C. and about 50% RH, and at least about 40 W/M² at about 35° C. and about 50% RH, and at least about 50 W/M² at about 35° C. and about 50% RH when tested according to the method described herein for heat loss and evaporative resistance, without providing a portable cooling unit to the garment. In still another embodiment an undergarment covering the torso of a wearer formed from a first impermeable barrier material with a panel of a second selectively permeable barrier material on a back garment surface, has a heat loss of at least 20 w/M², or at least 30 w/M², or at least 40 w/M², or at least 50 w/M² at about 35° C. and about 50% RH when tested according to the method described herein for heat loss and evaporative resistance.

Test Methods Air Permeability/Impermeability—Gurley Number Test

Gurley numbers were obtained as follows. The resistance of samples to air flow was measured by a Gurley densometer (ASTM) D726-58) manufactured by W. & L. E. Gurley & Sons. The results are reported in terms of Gurley Number, which is the time in seconds for 100 cubic centimeters of air to pass through 6.54 cm² of a test sample at a pressure drop of 1.215 kN/M² of water. A material is air-impermeable if no air passage is observed over a 120 second interval.

Moisture Vapor Transmission Rate Test

Moisture vapor transmission rates (MVTRs) were determined using the procedure set forth in U.S. Pat. No. 4,862,730 using potassium acetate as the salt and open pore expanded PTFE for the waterproof moisture vapor permeable membranes. These membranes nominally had a porosity of between 75% and 80%, with a thickness of approximately 0.04 mm. The environment was maintained at 50% relative humidity and 23° C. The water bath was maintained at 23° C.

Heat Loss And Evaporative Resistance

A thermal sweating torso was used in accordance with ASTM standards F1291 and F2370 to determine heat loss and evaporative resistance of the clothing ensemble. The only deviation form this standard test method was the shape of the torso and areas excluded from measurement. ASTM standards F1291 and F2370 utilize a full body mannequin. The present invention was tested using a mannequin torso without the arms and legs. This difference was accounted for in the evaporative resistance and heat loss calculations in which the values were divided by the actual surface area measured (normalized to a unit area) and reported as watts per square meter.

Chemical Penetration Resistance

Chemical penetration resistance was determined using the standard test method described in NFPA 1971 ASTM F903. All materials were tested in accordance with this standard procedure.

Packed Volume Test

The packed volume of the inventive constructs were determined using ASTM F1853-03 (Standard Test Method for Measuring Sleeping Bag Packing Volume) with the following departures from the specified apparatus/procedure: 1) test sample was an undergarment instead of sleeping bag; 2) smaller cylinder used: 13.97 cm diameter (5.5″); 3) compression weight used with smaller cylinder: 10.433 kg force (23 lbs)—this mimicked the same compression pressure generated with the standard cylinder and load.

A test rig was used comprising a ½″-thick Lexan cylinder measuring 5.5″ in diameter with an open top and a plunger that sits squarely upright in the cylinder and is not airtight with the walls of the cylinder. The plunger is removed from the cylinder, the test sample is inserted in the cylinder, and the plunger is placed in the cylinder on top of the sample. Weights are slowly added until a 23 lb load is reached. The weights are oriented so as to not touch the sides of the cylinder. If any of the weights are released rapidly, the test is nullified. Once the desired weight has been applied, a measurement is taken from the base of the cylinder to the bottom of the plunger in order to obtain the mean compressed height. The sample is then removed from the cylinder and fluffed prior to repeating the test. The test is repeated five (5) times and the data shall be averaged. The volume of the compressed material is calculated by multiplying the area of the plunger 0.0153 m³ (23.76 square inches) by the mean compressed height. Packing volume is reported in square inches (m³).

Suter Test for Water Entry Pressure

To determine whether a protective barrier fabric or the seams of a garment made from the protective barrier fabric are waterproof, the Suter test procedure is used, which is based generally on the description in ISO 811-1981. This procedure provides a low pressure challenge to the sample being tested by forcing water against one side of the test sample and observing the other side for indication that water has penetrated through the sample.

The sealed seam test sample is clamped and sealed between rubber gaskets in a fixture that holds the sample so that water can be applied to an area of the sample 3 inches in diameter (7.62 cm). The water is applied under air pressure of 3 psig (0.21 bar) to one side of the sample. In testing a fabric laminate, the water would be applied to the face or exterior side. In testing a sealed seam, water is applied to the face side of the sample and the opposite side, or seam backer layer, is observed for leaks.

The opposite side of the sample is observed visually for any sign of water appearing (either by wicking or the appearance of droplets) at the seam edge for 3 minutes. If no water is observed, the sample has passed the test and the sample is considered to have a water entry pressure greater than the 3 psig load at which the test was conducted.

Without intending to limit the scope of the present invention, the following examples illustrate how the present invention may be made and used.

EXAMPLES Comparative Example 1

A garment was constructed from an air impermeable, moisture vapor impermeable material, and tested for heat loss and evaporative resistance.

A garment top portion was constructed having greater than 95% of the surface area of the garment constructed from a 2-layer-laminate having a moisture vapor permeability of less than 900 g/(m²/day). The 2-layer laminate was constructed of a full density fluoropolymer film laminated to a polyester knit textile layer (1.4 oz/yd²), and passes the NFPA 1971 chemical penetration resistance test described above. The garment was constructed having the polyester knit textile layer facing away from and the film towards the body of the wearer. The fabric weight was about 3.5 oz/yd². The garment comprised a collar fascia made of cotton knit. The garment size corresponded approximately to an XL. The garment was tested on a thermal sweating mannequin at 35° C. and 50% RH. The heat loss and evaporative resistance results were calculated according to the method described above. Results are summarized in Table 1.

Example 2

A garment was constructed from a first barrier material comprising an air impermeable, moisture vapor permeable material and further comprising portions of a second barrier material comprising an air impermeable, moisture vapor permeable, and tested for heat loss and evaporative resistance.

A garment top portion was constructed having approximately 90% of the garment surface area of a 1.4 oz/yd², air impermeable, moisture vapor impermeable permeable 2-layer laminate comprising a knit textile layer adhered to a dense PTFE layer. The knit side of the two layer laminate was oriented to face away from the body of the wearer and the film was oriented towards the body of the wearer.

The garment further comprised a panel of a second barrier material which comprised a selectively permeable, air impermeable, moisture vapor permeable material comprising a polyamine polymer. The second barrier material was manufactured by W. L. Gore & Associates, Inc. (Elkton, Md.) under part number KSGZ103100A. The second selectively permeable barrier material was a 5.75 oz/yd², 3-layer laminate constructed having a nylon knit layer laminated with adhesive 44 and 44′ to each side of the selectively permeable membrane layer (FIG. 4). The 3-layer laminate had a moisture-vapor transmission rate of about 4,000 g/(m²*day) when measured according to the test described herein.

The second barrier material comprised about 10% of the garment surface area. A panel of the second barrier material measured about 0.17 m² and was located on the garment back surface corresponding to the upper back region of the test mannequin as illustrated in FIG. 2, at 40. The second barrier material panel replaced an area of the first barrier material in the construction of this garment sample. The second barrier material was integrally included as part of the garment construction and joined to the first barrier material by a seam (FIG. 2).

Both first and second barrier materials were sufficiently impermeable to pass the NFPA 1971 chemical penetration resistance test described above. The overall material weight of the garment having both first and second barrier materials was about 1.84 oz/yd². The garment size corresponded approximately to an XL.

The garment was tested on a thermal sweating mannequin, and results were calculated for heat loss and evaporative resistance according to the method described above. Results are summarized in Table 1.

TABLE 1 The water entry pressure, and heat loss were determined for garment top portions, and packed volume was measured for garment top and bottom portions, for Comparative Example 1 without any moisture vapor permeable panels and Example 2 which utilized moisture vapor permeable panels COMPARATIVE EXAMPLE 1 EXAMPLE 2 Water Entry >3.0 >3.0 Pressure (lbs/in²) Packed Volume 0.0024 M³ 0.0032 M³ Heat loss (w/m²) at 2 57 35° C./50% RH

While particular embodiments of the present invention have been illustrated and described herein, the present invention should not be limited to such illustrations and descriptions. It should be apparent that changes and modifications may be incorporated and embodied as part of the present invention within the scope of the following claims. 

1. An article comprising: an undergarment for use under casual clothing comprising; a garment surface covering arms, legs, and torso of a wearer and having i) about 55 to about 95% of the garment surface area formed from a first impermeable barrier material comprising air impermeable, moisture vapor impermeable fluoropolymer, and ii) about 5% to about 45% of a garment surface area formed from a second selectively permeable barrier material comprising an air impermeable, moisture vapor permeable expanded polytetrafluoroethylene (ePTFE) composite; wherein the second barrier material is located on a back garment surface corresponding to at least one of a back surface of a wearer's leg or torso; wherein the first and second barrier materials each passing NFPA 1971 ASTM F903 chemical penetration tests and each having a WEP≧3 psi.
 2. The article of claim 1 wherein the undergarment has a packed volume of less than 0.0042 m³.
 3. The article of claim 1 wherein the undergarment has a packed volume of less than 0.037 m³.
 4. The article of claim 1 wherein the undergarment has a packed volume of less than 0.0034 m³.
 5. The article of claim 1 wherein a front garment surface consists essentially of the first barrier material.
 6. The article of claim 1 wherein a panel of the second barrier material is on a garment torso back surface.
 7. The article of claim 1 wherein the second barrier material comprises a moisture vapor permeable, air impermeable ePTFE composite comprising a porous ePTFE layer and a monolithic polymer layer.
 8. The article of claim 7, wherein the monolithic polymer layer is polyurethane.
 9. The article of claim 7, wherein the monolithic polymer layer is a polyamine polymer.
 10. The article of claim 7, wherein the ePTFE composite comprises two porous ePTFE layers and the polyurethane therebetween.
 11. The article of claim 1 wherein the first impermeable barrier material comprises densified ePTFE.
 12. The article of claim 1 wherein the first impermeable barrier material is a laminate further comprising a textile layer.
 13. The article of claim 12, wherein the textile comprises a knit.
 14. The article of claim 1 wherein the second selectively permeable barrier material is a laminate further comprising a textile layer.
 15. An article comprising: an undergarment for use under casual clothing comprising; a garment surface covering arms, legs and torso of a wearer and having a heat loss of at least 20 w/M² at about 35° C. and about 50% RH, consisting essentially of i) about 85% to about 95% of the garment surface area formed from a first impermeable barrier material comprising air impermeable, moisture vapor impermeable polytetrafluoroethylene, and ii) about 5% to about 15% of a garment surface area formed from a second selectively permeable barrier material comprising an air impermeable, moisture vapor permeable expanded polytetrafluoroethylene (ePTFE) composite; wherein the second barrier material is located on a back garment surface corresponding to at least one of a back surface of a wearer's leg or torso; wherein the first and second barrier materials each passing NFPA 1971 ASTM F903 chemical penetration tests and each having a water entry pressure ≧3 psi.
 16. The article of claim 15 wherein the undergarment has a heat loss of at least about 30 w/M² at about 35° C. and about 50% RH.
 17. The article of claim 15 wherein the undergarment has a heat loss of at least about 40 w/M² at about 35° C. and about 50% RH.
 18. The article of claim 15 wherein the undergarment has a heat loss of at least about 50 w/M² at about 35° C. and about 50% RH.
 19. An article comprising: an undergarment for use under casual clothing comprising; a garment surface covering the torso of a wearer and having a heat loss of at least 20 w/M² at about 35° C. and about 50% RH, consisting essentially of i) about 85% to about 95% of the garment surface area formed from a first impermeable barrier material comprising air impermeable, moisture vapor impermeable polytetrafluoroethylene, and ii) about 5% to about 15% of a garment surface area formed from a second selectively permeable barrier material comprising an air impermeable, moisture vapor permeable expanded polytetrafluoroethylene (ePTFE) composite; wherein the second barrier material is located on a back garment surface corresponding to a wearer's torso; wherein the first and second barrier materials each passing NFPA 1971 ASTM F903 chemical penetration tests and each having a water entry pressure ≧3 psi.
 20. The article of claim 19 wherein the undergarment has a heat loss of at least about 30 w/M² at 35° C. and 50% RH.
 21. The article of claim 19 wherein the undergarment has a heat loss of at least about 40 w/M² at 35° C. and 50% RH.
 22. The article of claim 19 wherein the undergarment has a heat loss of at least about 50 w/M² at 35° C. and 50% RH. 